package com.compty.security.jcaptcha;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ImageCaptchaServlet extends HttpServlet {
	
	private static int WIDTH = 60;   
    private static int HEIGHT = 20;   
    private static int LENGTH = 4;
    /**
     * serial.
     */
    private static final long serialVersionUID = -1L;

    /**
     * 初始化.
     *
     * @param servletConfig ServletConfig
     * @throws ServletException servlet异常
     */
    public void init(ServletConfig servletConfig) throws ServletException {
        super.init(servletConfig);
    }
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    	
    	  HttpSession session = request.getSession();   
    	  
          response.setContentType("image/jpeg");   
   
          ServletOutputStream sos = response.getOutputStream();   
   
          //设置浏览器不要缓存此图片   
          response.setHeader("Pragma","No-cache");   
          response.setHeader("Cache-Control","no-cache");   
          response.setDateHeader("Expires", 0);   
   
          //创建内存图象并获得其图形上下文   
          BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_BGR);    
          Graphics2D g = image.createGraphics();   
   
          //产生随机的认证码   
          char [] rands = generateCheckCode();   
   
          //产生图像   
          drawBackground(g);   
          drawRands(g,rands);   
   
          //结束图像的绘制过程，完成图像   
          g.dispose();   
   
          //将图像输出到客户端   
          ByteArrayOutputStream bos = new ByteArrayOutputStream();   
          ImageIO.write(image, "JPEG", bos);   
          byte [] buf = bos.toByteArray();   
   
          response.setContentLength(buf.length);   
          //下面的语句也可写成：bos.writeTo(sos);   
          sos.write(buf);   
          bos.close();   
          sos.close();   
   
          //将当前验证码存入到Session或者数据库中,下一个表单处理中验证客户端提交的验证码是否正确   
          session.setAttribute("check_code",new String(rands));   
    }
    
    private static char [] generateCheckCode()   
    {   
       //定义验证码的字符表   
//       String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";   
       String chars = "0123456789";   
  
       char [] rands = new char[LENGTH];   
       for(int i=0; i<LENGTH; i++)   
       {   
          int rand = (int)(Math.random() * 10);   
          rands[i] = chars.charAt(rand);   
       }   
       return rands;   
    }   
       
    private void drawRands(Graphics g , char [] rands){   
          g.setColor(Color.BLACK);   
          g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));   
  
          //在不同的高度上输出验证码的每个字符            
          g.drawString("" + rands[0],1,17);   
          g.drawString("" + rands[1],16,15);   
          g.drawString("" + rands[2],31,18);   
          g.drawString("" + rands[3],46,16);   
//          g.drawString("" + rands[4],61,14);   
//          g.drawString("" + rands[5],76,19);   
  
//          System.out.println(rands);   
    }   
  
   private void drawBackground(Graphics g){   
       //画背景   
          g.setColor(new Color(0xDCDCDC));   
          g.fillRect(0, 0, WIDTH, HEIGHT);   
  
          //随机产生120个干扰点   
      for(int i=0; i<120; i++){   
         int x = (int)(Math.random() * WIDTH);   
         int y = (int)(Math.random() * HEIGHT);   
         int red = (int)(Math.random() * 255);   
         int green = (int)(Math.random() * 255);   
         int blue = (int)(Math.random() * 255);  
         
         g.setColor(new Color(red,green,blue));           
         g.drawOval(x,y,1,0);   
      }   
         
      //加两条干扰线   
      g.drawLine(0, 5, 90, 5);   
      g.drawLine(0, 15, 90, 15);   
   }   
    
}

